Image processing apparatus having processing operation by coordinate calculation

ABSTRACT

An image processing apparatus draws an image, stores the drawn image in a memory, reads image data from the memory along a raster direction, and executes a processing operation required for a display with respect to the read image data to output the processed image data to a display device. A display processing unit executes a processing operation including a coordinate calculation with respect to the image data read out along the raster direction. As a result, the image can be formed at high speed even under transition state of displayed images.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is based on and incorporates herein by referenceJapanese Patent Application No. 2001-261645 filed on Aug. 30, 2001.

FIELD OF THE INVENTION

[0002] The present invention generally relates to an image processingapparatus for executing a processing operation capable of drawing animage and of displaying the image on a display device. Morespecifically, the present invention is directed to a technique capableof displaying a pictorial image at high speed.

BACKGROUND OF THE INVENTION

[0003] Recently, there are many cases that operation menus and the likeare superimposed on pictorial images which constitute backgrounds anddisplayed. In order to apply high quality feelings, or high gradefeelings to object images such as these menus, not only simple switchingoperations of displaying, or not displaying these object images arecarried out, but also transition conditions must be made smooth, duringwhich these object images are switched from being displayed and notbeing displayed, and vice versa. In the case that such a transitioncondition is formed by way of a drawing operation, since images arerequired to be re-drawn with respect to each of frames, lengthy time isrequired.

[0004] A processing flow operation proposed in a related art is shown inFIG. 1B. A pictorial image is drawn by a drawing process unit 11. Thedrawn image data is stored into a predetermined storage position of amemory 13. When an image is to be displayed, the image data is read outfrom a predetermined storage position of the memory by a memory controlunit 16. This memory control unit 16 operates as an imageprocessing/synthesizing unit. Then, such a processing operation as anRGB converting operation and a simple image synthesizing operation iscarried out with respect to the read image data by a display processingunit 15. Thereafter, the processed image data is outputted to a displaydevice 17 at necessary timing. While the memory 13 is constituted by,for example, a VRAM (video random access memory), the display processingunit 15 sequentially reads out the image data along the raster directionto execute the display processing operation with respect to this memory13.

[0005] When an image to be displayed is changed, this image is re-drawnby the drawing unit 11 and then, the re-drawn image is stored in thememory 13. Then, the memory control unit 16 reads out this stored imagedata if required, and executes such a processing operation as the affinetransformation with respect to the read image data. Thereafter, theprocessed image data is stored in the memory 13. In the case that animage processing technique which is typically known as the affinetransformation is carried out, there are many possibilities thataddresses of read pixels are different from calculated addresses. As aresult, while an additional memory used to save images is separatelyprovided, the following operation is carried out. That is, a calculationresult obtained from the read pixel values is stored in a calculatedaddress of the additional memory.

SUMMARY OF THE INVENTION

[0006] It is therefore an object of the present invention to provide animage processing apparatus capable of producing images at high speedeven under such a transition condition of displayed images.

[0007] According to the present invention, an image processing apparatusdraws an image, stores the drawn image in a memory, reads image datafrom the memory along a raster direction, and executes a processingoperation required for a display with respect to the read image data tooutput the processed image data to a display device. A displayprocessing unit executes a coordinate calculation operation as theprocessing operation with respect to the image data read out along theraster direction. As a result, the image can be formed at high speedeven under transition state of displayed images.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] For a better understanding of the present invention, reference ismade to a detailed description to be read in conjunction with theaccompanying drawings, in which:

[0009]FIG. 1A is a schematic block diagram showing an image processingapparatus according to an embodiment of the present invention, and FIG.1B is a block diagram showing an image processing apparatus according toa related art;

[0010]FIGS. 2A to 2C are explanatory diagrams showing display examples,FIG. 2D is a production example of a compressed image, and FIG. 2E is aproducing example of an enlarged image with employment of a coordinatecalculation function realized by the image processing apparatus of theembodiment;

[0011]FIG. 3 is an explanatory diagram showing a production example ofan untialiasing image formed by the image processing apparatus of theembodiment;

[0012]FIG. 4A to FIG. 4C are explanatory diagrams showing productionexamples of a projection image formed by the image processing apparatusof the embodiment; and

[0013]FIG. 5 is an explanatory diagram showing a scrolling operation ofa birds-eye view formed by the image processing apparatus of theembodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0014] Referring now to FIG. 1A, an image processing apparatus of thisembodiment is provided with a drawing unit 11, memory 13, and a displayprocessing unit 15 for a display 17.

[0015] The drawing unit 11 draws image data in response to a commandentered from a control apparatus (not shown), and this drawn image datais written into the memory 13. The memory 13 may be a VRAM and the like.The display processing unit 15 reads out the image data from this memory13 along a raster direction, and performs an RGB converting operation,and executes a processing/synthesizing processing operation by thedisplay control means, if necessary, with respect to the read imagedata. Its outputs with respect to the display device 17 as appropriatetiming. It should also be noted that as the display device, forinstance, a liquid crystal display, a plasma display, a CRT, an organicEL, and the like may be positively employed.

[0016] In this embodiment, the display processing unit 15 contains aconverting unit 151, a demultiplexer 152, a spatial filter unit 153, anα blending unit 154, a coordinate calculating unit 155, and amultiplexer 153. This converting unit 151 converts image datarepresented by a color palette system into RGB data. The demultiplexer152 demultiplexes an input into three sorts of processing units, thatis, the spatial filter unit 153, the α blending unit 154, and thecoordinate calculating unit 155. The multiplexer 153 selects outputsfrom these respective processing units 153, 154, and 155.

[0017] Alternatively, the demultiplexer 152 may output the demultiplexedimage data to the multiplexer 153 without via these respectiveprocessing units 153, 154, and 155. Also, the display processing unit 15is arranged in such a manner that the output selected by the multiplexer153 is supplied to the display device, and also, is again entered intothe demultiplexer 152. Furthermore, the demultiplexer 152 may bearbitrarily controlled as to how this demultiplexer 152 demultiplexesthe input to which processing units 153, 154, and 155.

[0018] As a result, for instance, such an image data which has beenprocessed by either the spatial filter (SF) unit 153 or the coordinatecalculating unit 155 may be entered from the multiplexer 156 to thedemultiplexer 152, and then the image synthesizing operation may becarried out by the α blending unit 154. Alternatively, this image datamay be processed in a sequence opposite to the above sequence. Asapparent from the foregoing description, the image data may be processedthrough all of these three processing units 153, 154 and 155 in anarbitrary sequence. Furthermore, the image data may be processed throughthe same processing units plural times.

[0019] It should be noted that both the spatial filter unit 153 and thecoordinate calculating unit 155 operate to process image, and the αblending unit 154 operates to synthesize a screen.

[0020] In the case of the arrangement shown in FIG. 1B, thegeneral-purpose image processing/synthesizing technique such as theaffine transformation is carried out. In particular, when the imageprocessing operation is carried out, there are many cases that readingaddresses of a memory are different from outputting addresses of thememory. As a result, while additional memory used to save an image isseparately provided, the following operation is carried out. That is,the calculation result of the read pixel value is stored at thecalculated address of this additional memory.

[0021] These functions may contain a function capable of processingimage data along the raster direction, and/or may be substituted by aprocessing operation along the raster direction in a simple manner. Forexample, in case that rectangular image is converted into trapezoidalshape, if image is deformed by executing affine transformation, thenmemory addresses must be separately calculated one by one.Alternatively, this image deformation may be substituted by simplyperforming longitudinal and transverse thinning operation.

[0022] In contrast, in the image processing apparatus shown in FIG. 1B,since the image data which have been read from the memory 13 along theraster direction are processed/synthesized in the display processingunit 15, the image data are not required to be again written into thememory 13. As a result, the images can be produced at high speed. Forinstance, while a pixel value which is located along the rasterdirection and is required to display an image is employed for theprocessing operation, only such pixel values located around this pixelvalue are read out from the memory 13, and then, these read pixel valuesare converted into RGB data in the converting unit 151. Thereafter,these RGB data are stored in a buffer memory.

[0023] The spatial filter unit 153 executes the image processingoperation by using the peripheral pixel values with respect to such apixel value to be processed. Then, in the α blending unit 154, theimage-processed pixel data are synthesized with data which are notprocessed (for example, background image) so as to produce an outputimage. If the above image processing operation is carried out, then thedrawing operation by the drawing unit 11 is no longer required, but alsothe processed image data are not again stored in the memory 13, so thatthe high-speed image production can be realized.

[0024] Next, the α blending processing operation is described. This αblending processing operation means that when two sets of images aresynthesized with each other, a calculation is carried out by employingan a value indicative of transmittance. A formula of the α blendingprocessing operation is given as follows:

[0025] Pdisp=(1−α)×Pa+α×Pb, where

[0026] symbol “Pdisp” indicates a pixel value to be displayed;

[0027] symbol “Pa” shows a pixel value of a plane “a”;

[0028] symbol “Pb” denotes a pixel value of another plane “b”; and

[0029] symbol “α” indicates a ratio of transmittance when two sets ofimages are synthesized with each other.

[0030] As a consequence, in the case of α=1, only the plane “b” isdisplayed. In the case of α=0, only the plane “a” is displayed.

[0031] Also, in the case that a color palette system is employed,addresses of image data represented by way of the color palette systemare stored in the memory 13. As a result, these address data have nocorrelative relationship with respect to peripheral pixel values(address data), and generally, an image cannot be processed. However, inaccordance with the arrangement of this embodiment, the displayprocessing unit 15 reads out the image data from the memory 13, andexecutes the RGB converting processing operation. Thereafter, the imageprocessing operation may be applied to the RGB-converted image data.That is, the present invention may also be applied to the color palettetype drawing system.

[0032] Then, in the case of this embodiment, the image processingapparatus owns only three functions of spatial filter, coordinatecalculation, and α blending as the function blocks, which arerepresented as three processing units 153, 154, 155. The imageprocessing apparatus uses these function blocks by combining thesefunction blocks with each other. When the hardware structure of thedisplay processing unit 15 is considered, an increase in the circuitarea does not cause any serious problem.

[0033] It should also be understood that these functions may beindependently employed. For example, an object image may be moved, andan image may be deformed by executing only the coordinate calculation.Several examples of image processing/synthesizing operations executed bythe respective functions will be described as follows.

[0034] [Image Processing by Coordinate Calculation Function]

[0035] For instance, an image may be deformed to be similar to a wave,when it is assumed that a data position (x, y) used to read out imagedata from the memory by employing the coordinate calculation function isdefined as follows.

(x′, y′)=x+sin(y×2π×t _(—) buf/ROW)×y_buf

[0036] In the above equation, symbol “ROW” indicates a size of an imagealong a longitudinal direction, symbol “y_buf” indicates a ratio ofdeforming the image along a transverse direction, and symbol “t_buf ”indicates a ratio of deforming the image along a longitudinal direction.

[0037]FIGS. 2A shows an original image. FIG. 2B show an image formed inthe case of t_buf=2 and y_buf=8, and FIG. 2C show an image formed in thecase of t_buf=6, y_buf=8. As explained above, while the original image(FIG. 2A) is gradually deformed, if no image is displayed by combining,for instance, the blending function, then the image display may beachieved with having a high grade feeling in comparison with such animage display operation that the image is simply displayed and then notdisplayed.

[0038] [Compression of Image]

[0039] In the case that an original image is compressed, a readoutposition may be determined by simply employing only the coordinatecalculation function so as to thin the image. Alternatively, as shown inFIG. 2D, for example, while an averaging filter may be used as thespatial filter (SF), an image which is compressed based upon the averagevalue may be formed. In the example of FIG. 2D, the original image iscompressed by ⅓.

[0040] [Enlargement of Image]

[0041] In the case that an original image is enlarged, the originalimage may be enlarged with a high image quality by properly changing acoefficient of a spatial filter. For example, FIG. 2E shows such a casethat the original image is enlarged two times. A black-colored circleindicates an original pixel value, and a white-colored circuit indicatesa value which is determined by way of a filtering processing operation.While a 2×2 matrix is employed as a filter, when filter coefficients asindicated in this drawing are employed with respect to values of theoriginal image which are located in a rectangular region surrounded by adotted line in order to determine the respective white-colored circles,then the values of the original image can be interpolated in a linearmode. Thus, a high image quality can be achieved.

[0042] [Antialiasing]

[0043] In an artificial image such as an animation image, there are somepossibilities that a jagged edge (so-called “jagy”) is produced withrespect to an inclined line. As a method of correcting this “jagy”, anantialiasing method is used. Normally, an area having a size two, orthree times larger than a necessary area is drawn during drawingoperation, and an averaged value is outputted, so that the antialiasingmethod is carried out. This is referred to as a “super sampling system.”However, in this super sampling system, since the area larger than thatof the actual case is drawn, processing time thereof is considerablyincreased.

[0044] As a consequence, in this embodiment, the antialiasing method iscarried out as indicated in FIG. 3. First, while a differential typefilter is employed as a spatial filter 1 (SF1), an edge is detected.Also, while an averaging filter is used as a spatial filter 2 (SF2), a“blurred” image is produced. Since there are large possibilities that aso-termed “jagy” is produced at a peripheral portion of an edge, a“blurred” image is used, and the original image is directly left atportions other than this edge portion. In accordance with thisantialiasing method, only the edge portion is blurred, so that theeffect of the antialiasing method may be achieved.

[0045] [Forming of Projected Image]

[0046]FIGS. 4A to 4C show a case that only data of required coordinatevalues are acquired by executing the coordinate calculation so as toproduce an image. That is, an effect of an image projection can beachieved by merely thinning the image data. A perspective feeling may befurthermore increased in such a manner that while a thinning method isadaptively changed from a depth direction up to a forward direction, thethinning amount is further increased along the depth direction.

[0047] [Quasi-Birds-Eye View]

[0048]FIG. 5 indicates such a case that a quasi-birds-eye view is formedfrom a two-dimensional map image by employing a method of producing aprojection image. While a two-dimensional map image may be scrolled bymerely changing a readout position, a similar method to that ofscrolling of the two-dimensional map image cannot be employed toscrolling of a birds-eye view. As a result, such a birds-eye view mustbe again drawn for every frame. To the contrary, in accordance with thearrangement of this embodiment, scrolling of the birds-eye view may becarried out by employing a similar method to that of scrolling of thetwo-dimensional map image, so that the birds-eye view can be displayedin the high-speed scrolling manner.

[0049] Specifically, an area larger than a display area is drawn by thedrawing unit 11 similar to the case when the two-dimensional map imageis scrolled ((a) in FIG. 5), and then the image data of the drawn areais stored in the memory 13. Then, in the case that a birds-eye view isformed, image data required to display the birds-eye view is read outfrom the memory 13, and then, a deformation processing operation iscarried out with respect to this read image data so as to produce abirds-eye view in the display processing unit 15. Since a thinningprocessing operation is employed in the deformation processingoperation, an image after being deformed becomes small. As aconsequence, image data corresponding to a larger area is read out fromthe memory 13 ((b) in FIG. 5). Thereafter, the following modificationprocessing operations 1 to 3 are carried out with respect to the readimage data.

[0050] In the deformation processing operation 1, the readout image iscompressed along a longitudinal direction by executing a thinningprocessing operation. In this case, the following thinning methods maybe conceived. That is, for instance, the readout image may be thinned ina uniform manner. Alternatively, a thinning ratio of an upper portion ofthe readout image may be increased, whereas a thinning ratio of a lowerportion of the read image may be decreased.

[0051] In the deformation processing operation 2, with respect to animage which has been compressed along the longitudinal direction, athinning ratio from a lower portion to an upper portion of this imagemay be increased, so that a trapezoid-shaped image may be formed.

[0052] In the deformation processing operation 3, an area having a shape(rectangular shape in this case) corresponding to a figure of a displayscreen is cut out from the trapezoid-shaped image ((c) in FIG. 5).

[0053] In this embodiment, when this deformation processing operation iscarried out, only image data required to be converted/displayed arethinned with respect to the image data read along the raster direction,and the thinned image data are directly outputted along the rasterdirection in the coordinate calculating unit 155. That is, while “imagedata are thinned along longitudinal direction”, “image data are thinnedalong transverse direction”, and also “necessary area is calculated”,only image data which are finally required may be employed.

[0054] Then, since this cut image is synthesized with an object image ofa sky, a quasi-birds-eye view may be formed ((d) in FIG. 5).

[0055] As a consequence, the two-dimensional map image stored in thememory 13 are sequentially read out by changing the readout positionsthereof, and then, the readout two-dimensional map images are processedto form the above quasi-birds-eye view image. Thus, the quasi-birds-eyeview image to be displayed can be formed at high speed, and can bescrolled in a smooth manner.

[0056] It should also be noted that in a birds-eye view image, in orderto represent a perspective feeling, such a method may become effectivein which a mist scene appears as long as a viewer goes. To this end,while employing the α blending function, a gradation image may beproduced in which a map image can be clearly viewed in a lower portionof the screen, and a map image in the vicinity of the horizon within thebirds-eye view appears blurred.

[0057] [Others]

[0058] (1) When the image processing operation is carried out, theamount of data which are processed is relatively large, so that such animage processing operation may be carried out by executing a “pipelineprocessing operation.” As a result, the display processing unit 15 isequipped with plural sets of raster buffers which correspond to cyclesrequired to execute the image processing operations. One raster bufferis employed so as to process one image data. Then, while the imageprocessing apparatus is arranged in such a manner that one image datacan be outputted within a predetermined cycle by processing the imagedata in the pipeline manner, the synthesizing timing of the image datawhich is not processed may be preferably made coincident with thesynthesizing timing of the data which has been processed.

[0059] (2) As previously described, since the processing/synthesizingprocessing operation is carried out by the display processing unit 15with respect to the image data which are read out from the memory 13along the raster direction, the rewriting operation of the image datainto the memory 13 is no longer required which is needed in the relatedart. As a result, the image can be produced at the high speed. However,if the image is redrawn by the drawing unit 11, then the image havingthe high quality may be easily obtained. As a consequence, while theprocessing/synthesizing processing operation may be carried out by thedisplay processing unit 15 only under such an image transitioncondition, the image data may be preferably redrawn by the drawing unit11 under the normal condition, that is, not under such an imagetransition condition.

[0060] It should also be noted that when the display state under thetransition mode is switched to the display state under the normal mode,or when the display state under the normal mode is switched to thedisplay state under the transition mode, a sense of incongruity mayoccur in displayed images, because the images are different from eachother between the normal mode and the transition mode. In order to avoidthe occurrence of this incongruity sense, the α blending operation isexecuted by an α blending unit 154 of the display processing means. Thatis, in a case that the display mode is switched from the normal mode(drawn image is displayed) to the transition mode (image processed bydisplay processing unit 15 is displayed), otherwise, the display mode isconversely switched from the normal mode to the transition mode, boththe images obtained before/after the display mode is changed areprocessed by the α blending processing operation.

[0061] While one-screen data amount of image data is left in the memory13, if the display mode is changed, then both the images which has beenformed by executing the drawing operation (by drawing process block 11),or by the processing operation (by display processing unit 15) after themode change, are processed by the α blending processing operation so asto smooth the transitions of the displayed images. As a result, it ispossible to avoid the occurrence of such an incongruity sense duringmode transitions.

[0062] In this case, the mode switching operation may be conceived basedupon an externally-supplied signal. For example, it is so conceivablethat the image processing apparatus of the above embodiment is appliedto a navigation system. If so, then this image processing apparatus maydetermine whether the present operation mode corresponds to the normalmode, or the transition mode in response to an instruction signalsupplied from a navigation control unit capable of controlling theentire system.

What is claimed is:
 1. An image processing apparatus comprising: drawingmeans for drawing an image; storage means for storing therein the imagedrawn by the drawing means; and display processing means for readingimage data from the storage means along a raster direction, and forexecuting a processing operation required for an image display withrespect to the read image data to output the processed image data to adisplay device, characterized in that the display processing meansexecutes a processing operation including a coordinate calculation withrespect to the image data read out along the raster direction.
 2. Theimage processing apparatus as in claim 1, characterized by furthercomprising: mode switching control means for switching a processing modein the drawing means and also a processing mode in the displayprocessing means based on whether image processing is operated underimage transition state, wherein the mode switching control meansexecutes a transition mode processing operation which performs both theprocessing operation and a screen synthesizing processing operation,when the image processing operation is operated under the imagetransition state, and wherein the mode switching control means executesa normal mode processing operation in which a processing operationcorresponding to the processing operation executed by the displayprocessing means in the transition mode processing operation is carriedout by the drawing process means and the display processing meansexecutes a normal mode process which performs the screen synthesizingprocessing operation with respect to the image data, when the imageprocessing operation is operated under a state other than the imagetransition state.
 3. The image processing apparatus as in claim 2,further characterized in that, in a case that the processing operationin the transition mode and the processing operation in the normal modeare switched, the display processing means performs the screensynthesizing processing operation with respect to both images in such amanner that the image obtained by the processing operation before themodes are switched is advanced to the image obtained by the processingoperation after the modes are switched in a smooth manner.
 4. The imageprocessing apparatus as in claim 1, characterized in that the displayprocessing means outputs processed/synthesized image data to the displaydevice and also the storage means, and the storage means stores thereinthe image data after being processed/synthesized.
 5. The imageprocessing apparatus as in claim 1, further characterized in that: thedrawing means draws an image which is represented by a color palettesystem, and the image represented by the color palette system is storedin the storage means; and the display processing means converts theimage data which is read out from the storage means along the rasterdirection from color palette data into RGB data, and thereafter executesboth the processing operation and the screen synthesizing processingoperation with respect to the RGB data.
 6. The image processingapparatus as in claim 1, further characterized in that: the displayprocessing means includes a buffer means having a smaller storagecapacity than an image storage size of the image drawn by the drawingmeans; the display processing means reads the image data from thestorage means in a raster sequence required for the display, and alsoreads data around the image data required for the image display to storethe read data into the buffer means; and the display processing meansexecutes the processing operation by employing both the image data and'the data around the image data.
 7. The image processing apparatus as inclaim 6, further characterized in that the buffer means is capable ofstoring therein image data which are required to display several linesof images.
 8. The image processing apparatus as in claim 1, furthercharacterized in that the display processing means includes: an imageprocessing unit; an image synthesizing unit; a demultiplexer capable ofdemultiplexing inputs to both the image processing unit and the imagesynthesizing unit; and a multiplexer capable of selecting outputs fromboth the image processing unit and the image synthesizing unit, whereinan output derived from the multiplexer is again applied to thedemultiplexer.
 9. The image processing apparatus as in claim 8, furthercharacterized in that the image synthesizing unit of the displayprocessing means has a blending function of plural images based upon anequation defined as an output pixel value=first image datavalue×blending coefficient+second image data value×(1−blendingcoefficient).
 10. The image processing apparatus as in claim 1, furthercharacterized in that: the display processing means has plural sets ofbuffer means capable of processing one image data, which are required toexecute processing operation; the display processing means executes apipeline processing operation so that one image data can be outputtedwith a predetermined cycle; and synthesizing timing of image data whichis not processed is made coincident with synthesizing timing of imagedata which has been processed.
 11. The image processing apparatus as inclaim 1, further characterized in that the display processing means iscapable of executing each of a spatial filtering function, a coordinatecalculating function and a blending function, and executes a processingoperation by combining the three functions with each other.
 12. Theimage processing apparatus as in claim 11, further characterized in thatthe display processing means moves an object image, andrepresents/deletes the object image by employing both the coordinatecalculating function and the blending function.
 13. The image processingapparatus as in claim 11, further characterized in that, while thedisplay processing means uses the coordinate calculating function, thedisplay processing means compresses an image by selecting image datawhich is read out from the storage means.
 14. The image processingapparatus as in claim 11, further characterized in that the displayprocessing means further has a down-sampling function, and compresses animage so that the image data which are sequentially read out from thestorage means are thinned at a predetermined rate.
 15. The imageprocessing apparatus as in claim 11, further characterized in that,while the display processing means employs the spatial filter function,the display processing means compresses an image by applying an integraltype filter to the image data read out from the storage means.
 16. Theimage processing apparatus as in claim 11, further characterized in thatthe display processing means further has an up-sampling function, andenlarges an image so that a zero-th hold processing operation is carriedout with respect to the image data which are sequentially read out fromthe storage means, while the same data are inserted into the read imagedata in a predetermined ratio in the zero-th hold processing operation.17. The image processing apparatus as in claim 11, further characterizedin that, while the display processing means employs the spatial filterfunction, the display processing means enlarges an image by changing aspatial filter coefficient applied to the image data read out from thestorage means.
 18. The image processing apparatus as in claim 11,further characterized in that: while the display processing meansemploys the spatial filter function, the display processing meansapplies a differential type filter with respect to the image data readout from the storage means so as to extract an edge thereof, and furtherapplies thereto an integral type filter to obtain a blurred image; andthe display processing means executes a processing operation capable ofachieving an antialiasing effect by synthesizing the blurred image withthe relevant image which is not processed by using the information as tothe extracted edge.
 19. The image processing apparatus as in claim 11,further characterized in that, while the display processing meansemploys the coordinate calculation function, the display processingmeans acquires a projection image by thinning the image data which areread out from the storage means.
 20. The image processing apparatus asin claim 19, further characterized in that the display processing meansdetermines a thinning ratio based upon a projection angle of the image,and furthermore increases an effect of a perspective feeling byadaptively changing thinning ratios on the close side to a view pointand the far side to the view point.
 21. An image processing apparatus asin claim 1, further characterized in that, while a two-dimensional mapimage is stored into the storage means, the display processing meansforms an image having a perspective feeling by projecting thetwo-dimensional map image read out from the storage means, and thenproduces a quasi-birds-eye view in such a manner that a portion of theimage having the perspective feeling is cut out, and the cut-out imageportion is synthesized with an object image indicative of a sky.
 22. Theimage processing apparatus as in claim 21, further characterized inthat: the drawing process means draws the two-dimensional map imagehaving an area which is wider than a display area to be displayed on thedisplay device, and then stores the drawn two-dimensional map image inthe storage means; and the display processing means sequentially readsout a portion of the two-dimensional map image stored in the storagemeans by changing a readout position thereof, forms an image having aperspective feeling by projecting each of the readout images, andexecutes a scrolling display processing operation of a quasi-birds-eyeview in such a manner that a portion of the projection image is cut out,and the projection image portion is synthesized with the object image ofthe sky.
 23. A program which causes a computer to execute a function ofthe image processing apparatus as recited in claim 1.